The present invention generally relates to a device and method for delivering an expandable endoluminal prosthetic device, such as a stent, and more particularly to a device and method for placing a bifurcated stent such that only a single incision into a patient need be made.
Expandable surgical devices, such as stents and angioplasty balloons, are used in a variety of places in the human body to support various anatomical lumens, such as blood vessels, respiratory ducts, gastrointestinal ducts and the like. Conventionally, these devices are deployed in regions of stenosis or constriction in the target body lumen to hold the lumen open, thus obtaining a patent lumen and preventing immediate or future occlusion or collapse of the lumen and the resultant obstruction of fluids flowing therethrough. Because stent and balloon implantation is a relatively non-invasive procedure, it has proven to be a favorable alternative to surgery in, for example, certain cases of vascular stenosis. Bifurcated devices, with their trunk and branching configuration, are particularly well-suited for use in branching body lumen systems, such as in the coronary vasculature (which include the right, left common, left anterior descending and circumflex arteries and their branches) and the peripheral vasculature (including branches of the carotid, aorta, femoral, popliteal, and related arteries). Placement of such a bifurcated device can be rather complicated, often involving approaching the bifurcated section of the artery through at least two side branches or through the trunk plus one side branch. This procedure can be not only time-consuming, but also lead to more incision sites in the patient""s body, as well as necessitate more complicated maneuvers for the surgeon. Procedures for placement of a bifurcated stent are described in U.S. Pat. No. 5,720,735 to Dorros, entitled xe2x80x9cBifurcated Endovascular Catheterxe2x80x9d and U.S. Pat. No. 4,994,071 to MacGregor, entitled xe2x80x9cBifurcating Stent Apparatus and Methodxe2x80x9d. In these patents, which are representative of the state of the art, each of the branches has a dedicated guide wire to guide the placement of balloons, stents, stent grafts or grafts into a bifurcated anatomical lumen. This redundancy can lead to increases in the overall size, cost and complexity of delivery devices.
Accordingly, there exists a need for an apparatus used to place bifurcated stents and related surgical devices into a body lumen such that simpler surgical procedures are enabled, with a concomitant decrease in incision number or size and related invasive steps, thereby reducing patient trauma associated with complex medical procedures.
This need is met by the present invention, where the placement of a stent becomes simplified by the use of a single delivery catheter, using only a single incision in only one location. The present apparatus and method allow for placing non-bifurcating stents in a side branch of a bifurcating lumen, as well as for placement of all kinds of bifurcating stents anywhere in the body, with or without a graft. While it can be readily appreciated that the device described herein is applicable for use in numerous endoluminal devices, and in a variety of bifurcated body lumens, much of the subsequent discussion is limited to the example of a bifurcated stent for use in preventing an abdominal aortic aneurysm (hereinafter referred to as triple A), where such a device is commonly known as a triple A graft stent. Such a stent includes a near side branch section, far side branch section, and a trunk section joined to adjacent, or hinged ends of the two branch sections. Furthermore, it will be appreciated that the expansion of the triple A graft stent and related stents can be effected by plastic deformation due to balloon pressure, or triggering of elastically stored energy in the stent (such as with bistable stents or elastic or superelastic expansion).
According to an embodiment of the present invention, a catheter for inserting, deploying and removing a bifurcated surgical device is disclosed, where preferable surgical devices include bifurcated endoluminal stents, stent-grafts, grafts and balloon angioplasty mechanisms. The catheter, with an elongate hollow body, narrow proximal end and widened distal end is insertable into a single percutaneous incision site. The hollow body houses a central catheter wire that is used to deploy a stent mounted to the catheter. The distal end of the elongated body includes a flanged, exaggerated generally cylindrical portion configured to sheath the ends of the branch sections of the bifurcated stent, thus ensuring a small cross-sectional area for the entire as-inserted combination. The central catheter wire includes two leg portions connected at a common end to a trunk portion. The two leg portions of the central catheter wire are biased to a closed position, so that they are in a substantially side-by-side, parallel relationship, both effectively parallel with the trunk portion. This bias is important for establishing a small cross sectional area of the wire once the stent has been deployed. In stents that rely on balloons for expansion, this bias in the central catheter wire also helps to bring the deflated balloons together for improved ease of catheter removal. Prior to the deployment of the bifurcated surgical device, the bias is designed to be overcome by inherent spring forces in the branches of the bifurcated surgical device, which needs to expand to approximate the angle formed between the main and branching body lumens. This bias in the bifurcating surgical device is such that a substantially Y-shaped intersection is formed, which also induces the catheter to assume such a shape upon unsheathing of the bifurcating surgical device.
The coaxial arrangement between the components of the present system and the stent, as well as the relative axial movement between them permit both simple operation coupled with unobtrusive cross-sectional dimensions. Operability is further enhanced by the inclusion of position-indicating markers with steerable features. In addition to providing indicia of stent axial (or translational) position relative to the catheter, these markers provide readily-apparent indicia of the angular position of the device vis-à-vis the body lumen to enable accurate positioning of the stent. To enhance patient safety, the catheters of each of this and the following embodiments may optionally include a flexible housing that can follow the angular movements between the branches easily, while it smoothens the functioning of the device.
Alternately, the apparatus can be adapted to accept self-expanding stents, where the bifurcated balloon is replaced by multiple travelling sheaths that work in cooperation with tension and pushing elements within the catheter for removal of the sheaths from the stent surface. In this configuration, an additional wire, called a sheath deployment wire, is disposed adjacent the central catheter wire in the same hollow portion of the elongate body. The two wires work in conjunction with one another, as the sheath deployment wire is used to push the self-expanding stent and one or more of the stent-restraining travelling sheaths farther into the aorta such that the stent and sheaths are entirely beyond the body lumen bifurcation point. As previously discussed, the stent branches are of such spring bias that their tendency to splay is greater than the ability of the central catheter wire leg portions to stay together. This bifurcation allows one of the stent branches to be positioned in each of the iliac arteries upon partial pullback of the stent. Once the pullback has been accomplished, and the stent sheaths have been seated adjacent the body lumen bifurcation point, the central catheter wire, which now includes a series of mechanical stops along its trunk section, can be translated relative the stent such that it engages the travelling sheaths surrounding the far side branch and the trunk, moving them away from their corresponding stent sections, and permitting the stent to expand under its own elastic power. Once this is completed, the near side branch sheath can be removed by pulling back on the sheath deployment wire to allow expansion of the final stent section, at which time the catheter can be withdrawn therethrough, and out the incision.
According to another embodiment of the present invention, a catheter used for the deployment of a self-expanding surgical device is similar in structural attributes to the aforementioned alternate embodiment catheter, with an additional biasing sleeve to facilitate removal of the sheath and wire once the surgical device has been inserted. This results in a sandwich-like structure that surrounds the surgical device, and includes the central core catheter wire inside the inner surface of the self-expanding surgical device, a travelling sheath surrounding the outer surface of the surgical device, and a biasing sleeve disposed on the outer surface of the travelling sheath. Once the crush-resistant surgical device is pushed out from the travelling sheath and deployed in the body lumen, the contracting force of the biasing sleeve causes the travelling sheath to collapse into a smaller diameter, coming to rest substantially on or adjacent the central catheter wire. This reduced cross-sectional area makes it easier to remove the sheath and wire through the hollow inner core of the now-expanded surgical device without snagging or otherwise inadvertently engaging the surgical device.
According to another embodiment of the present invention, a catheter for delivering a non-branching stent can be placed into a side branch of a body lumen for situations where the catheter side branch makes an acute angle from the main lumen insertion direction, thereby overcoming the difficulty with which conventional catheters have had in reaching such a side branch. In this configuration, the main catheter, in contrast to the previous embodiment, does not have an elongate hollow body, instead comprising a core wire, sheath and sheath deploying wire. The core wire is further defined by a main body portion and a leg portion, where the main body portion extends from a user-graspable proximal end to a distal end, and the leg portion is hingedly attached to the main body portion""s distal end and configured for transporting the stent. The inherent spring stiffness at the distal junction is such that the leg and main body portions are biased in an open position to form an acute angle roughly commensurate with the angle made between the main body and side branch lumens. The angled bias between the distal end of the core wire""s main body portion and the joined leg portion can be overcome such that the remote end of the leg portion is pointing substantially toward the proximal end of the main body portion. In this compressed state, the cylindrical, substantially hollow sheath can be inserted over the distal junction, thus holding the main body and leg portions of the core wire in a substantially parallel configuration. The stent can be inserted over the remote end of the leg portion that protrudes beyond the open end of the sheath. As with the previous embodiments, the stent can be either self-expanding or balloon expandable. In the balloon-expandable variant, the core wire could be of hollow tubular structure to permit the passage of an expansion fluid or an additional wire therethrough. The use of a central catheter wire, surrounded by the thin-walled tube with high flexibility (made from, for example a superelastic Nitinol) is but one example. A catheter with such a tubular core wire has more longitudinal rigidity and gives a better support for accurate relative movements between the central catheter wire and the delivery sheath. Proximal actuation using such a configuration becomes much more controllable, thus facilitating the user""s task.
According to another embodiment of the present invention, a stent delivery catheter comprising an elongate body, central catheter wire and a stent release wire is disclosed. The elongate body includes a proximal end, a distal end sufficiently enlarged relative to the proximal end so as to sheath an engaging end portion of a stent, and a hollow core extending between the proximal and distal ends. The central catheter wire fits through the hollow core, and is positionable relative to the hollow core. The central catheter core wire is made up of a main body portion with a user-graspable proximal end and a distal end, and a leg portion comprising a distal end joined to the distal end of the main body section to form a hinged relationship therebetween and a remote end engageable with the stent. The stent release wire is disposed within and positionable relative to the hollow core in much the same way as the central catheter wire. The stent release wire is defined by a main body portion with a user-graspable proximal end and a distal end configured to engage the stent and the remote end of the leg portion. As with the previous embodiment, the central catheter wire may be of hollow tubular construction to permit the placement of another wire or fluid supply line therein.
According to yet another embodiment of the present invention, a method for inserting a bifurcating surgical device, such as a stent, is disclosed. The method includes bringing the stent into place by advancing the whole stent in a delivery catheter with restraining sheath through a single incision location. By way of example, this single incision could be through a main side branch artery in a patient""s leg. The distal end of the delivery catheter holding the stent is inserted until it arrives adjacent the aneurysm area, with the lower ends of the stent branch sections beyond the body lumen bifurcating point, where the aorta divides itself into the two common iliac arteries. Upon insertion beyond this bifurcating point, a restraining sheath is pulled back, thereby exposing the unconnected ends of the two branch sections. The stent is still in its unexpanded state, but the elasticity of the two branch sections of the stent tends to create an angle between the two hingedly connected branch sections. In the present context, two or more members are considered to be hingedly connected when they are joined at a common end, regardless of how they are attached, such that only relative rotational movement (with no translational component) is permitted at such connected end, while the opposing unconnected ends are free to move relative to one another, constrained only by resistive forces operating at the connected end. A resiliently biased connection could include hingedly connected members that exhibit elastically deformable properties such that upon removal of a constraining force, the members would revert back to a predetermined unconstrained spacing relative to one another. By proper engineering choice of the elastic force, the amount of spread between the unconnected ends of the branch sections is such that they can gently be pulled back into their respective arteries, while the trunk section of the stent is also pulled back into the final artery section, where the aneurysm is located.
Once the stent is properly positioned relative to the iliac arteries and the lower aorta, the whole stent can be expanded into the final shape, by, for example, either self-expansion features integral to the stent, or by a conventional expander (typically a balloon) located within the delivery catheter. In the former case, the stent may be made of a shape-memory material. In the latter case, the balloon can either be made from one single piece, with the same overall shape as the bifurcated stent, or from several sections that can be inflated at different times. With such a bifurcated balloon, the whole stent can be expanded without repositioning of the balloon and, if needed, can be done very fast, thus reducing critical operation time. After deflating, the balloon can then be moved in the catheter insertion (distal) direction until the free end of the far side leg portion is moved completely beyond the body lumen bifurcation point and into the trunk section of the aorta. The two branch sections of the bifurcating balloon have been made elastic as well, but in a different way than the branch sections of the stent, such that they are biased to a substantially parallel orientation in line with the trunk of the balloon. One way this biasing can be achieved is by using two elastic spring wires, strips or tubes made from straight superelastic Nitinol, or related shape-memory material, disposed either in or outside the center of the balloon branch sections, coming together in or near the center of the balloon trunk. Thus, in addition to the two opposing bias forces previously discussed, where the branch sections of the stent have to move apart for placement and the leg portions of the central catheter wire have to move together for easier removal, the presence of the balloon bias further reinforces the closing tendency of the catheter so promote the small cross-sectional area necessary to ensure ease and safety of catheter removal. Thus, once the stent has been deployed, and the catheter with the deflated balloon has been pushed into the trunk section of the aorta, the balloon branch sections snap back to their parallel position and the whole catheter with the deflated balloon can be withdrawn from the body through the incision site. For additional safety and reduction of the pull-out force required, the exaggerated distal end of the catheter""s elongate body can re-sheath the two leg portions of the central catheter wire that engage the branch sections of the balloon. An elastic sleeve can optionally be used to surround the balloon, thereby minimizing the balloon geometry after deflation by applying a biasing load on the balloon. This acts to decrease deflation time, as well as control the timing of inflation over the balloon length or influence the final dimensions during and after inflation.
According to still another embodiment of the present invention, a method of inserting a side branching stent is disclosed. After the stent is brought beyond the body lumen bifurcation point, the restraining sheath that held the wire sections parallel is removed by pushing farther into the distal direction. The natural bias of the distal junction then forces the predisposed angle between the core wire""s main body and leg portions. Once the angle inherent in the spring bias is established, the catheter is pulled back in proximal direction, causing the catheter to enter the side branch of the lumen that has to be treated. After deployment of the stent, the catheter is pushed into the initial direction of insertion until the remote end of the leg portion is again beyond the body lumen bifurcation point. The catheter sections are then brought into their parallel position by reinsertion into the sheath, and then the whole device is pulled out through the initial insertion location.
The catheter used to insert the side-branching stent can include an elongate hollow body, a core wire and a release wire. In this configuration, the central catheter core wire may be of hollow tubular construction (as hereinbefore discussed in conjunction with previous embodiments) to permit the placement of at least the release wire or a fluid supply line (if needed) therein. Such an arrangement promotes both relative motion between the components, as well as small footprint of the stent deployment mechanism.
Other objects and advantages of the invention will become more apparent after reference to the following description, the accompanying drawings and the appended claims.